The invention relates to a device for connecting metallic materials, in particular electrical conductors such as flexible cables, by means of ultrasound with a transducer which generates ultrasonic oscillations of a wavelength lambda and containing a sonotrode with a sonotrode head, as well as a converter, wherein the transducer is seated at a distance of at least lambda/4 in respect to the sonotrode head.
Conventional transducers for generating ultrasonic oscillations comprise a converter for converting electric oscillations into ultrasonic oscillations of a desired frequency and amplitude, a booster, as well as a sonotrode with a sonotrode head having an electrode, or respectively a work surface, wherein the contact with the materials to be welded takes place for welding metal elements, such as flexible cables. Since the welding surface, or respectively the welding point, extends parallel in respect to the sonotrode oscillation axis, the seating must not only absorb axial and radial forces, but also bending moments.
In this connection it is known to seat a transducer, comprising a converter, a booster and a sonotrode, in oscillation nodes extending in the booster as well as in the sonotrode. This in turn means a long structure of the transducer.
With a booster-less embodiment of a transducer, which therefore only contains a converter and a sonotrode, a partition can be formed between the converter and the sonotrode, in which a diaphragm spring is clamped, by means of which the transducer is seated. Moreover, a support in the oscillation node (FIG. 9) extending in the sonotrode is provided. In this case the diaphragm spring extends in the oscillation maximum. Not only is a radially large structure necessary because of the use of the diaphragm spring, but also an axially flexible seating. In connection with a further booster-less oscillation embodiment, seating is provided in the oscillation neutral point in the converter, as well as support in the oscillation zero point of the sonotrode (FIG. 10). It has been found here that the zero point seating in the converter leads to considerable problems.
In connection with a further known transducer, which includes a converter, booster and sonotrode, the booster and the sonotrode are respectively seated, or respectively supported, in the oscillation zero point (FIG. 7). The use of the booster results in a long structure. Moreover, transducers are known having partitions between the converter and the booster on the one hand, and the booster and the sonotrode on the other hand, from which diaphragm spring extend (FIG. 8). Since seating takes place in the oscillation maximum, the transducer is very flexibly supported. In addition, a large radial structure results because of the diaphragm spring used.
A device of the type known at the outset is known from DE 35 08 122 C2. Here, the sonotrode is supported by a plurality of locking screws, which are aligned perpendicularly in relation to the longitudinal axis of the sonotrode, which themselves do not absorb the occurring axial and radial forces, as well as bending moments, to the required degree. It is therefore necessary to additionally support the converter or booster. In actual use this takes place in the booster.